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31.
Krishna Gopal Dongol M. Cristina Melo e Silva Kouki Matsubara Taisuke Matsumoto Shuntaro Mataka Thies Thiemann 《无机化学与普通化学杂志》2003,629(6):945-947
The preparation of two η6‐estra‐1, 3, 5(10), 6‐tetraene tricarbonylchromium complexes 4 and 6 are described. In both cases only one stereoisomer can be isolated, in contrast to other estrane‐tricarbonylchromium complexes, where complexations are non‐stereoselective. X‐ray crystal structural analysis of 4 discloses that only the more sterically hindered β‐facial isomer is formed. It is assumed that the 6, 7‐olefinic moiety exerts a directive influence on the complexation. 相似文献
32.
Joo Bosco P. Da Silva Mozart N. Ramos 《International journal of quantum chemistry》1992,43(2):215-219
Ab initio MP 2/4-31G ** calculations indicate that the most stable form of C3NH is bent and singlet and that the linear structure corresponds to a maximum. The effect of changing the CNH angle on the total energy is slight, but it is quite pronounced on the molecular polarity. The wider angle tends to increase the polarity of C3NH. MP 2/4-31G ** calculations predict a difference of polarity between linear and bent structures of 0.8 D. 相似文献
33.
John F. Callan A. P. De Silva R. C. Mulrooney B. Mc Caughan 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):257-262
Summary This review highlights recent advances in the use of quantum dots (QD’s) as luminescent sensors. The bulk of the study concentrates
on systems that possess organic ligands bound to the surface of QD’s. These ligands vary from low molecular weight thiols
to larger molecules such as maltose binding protein. All have one thing in common: when a target analyte binds to the ligand/receptor,
a perturbation of the system occurs, that registers itself as a change in the luminescence intensity of the QD. Two main mechanisms
are prevalent in controlling the luminescent intensity in such systems. The first is Photoinduced Electron Transfer (PET)
and the second energy transfer. This review looks at current sensors that operate by using these mechanisms. Two component
systems are also investigated where a quencher is first added to a solution of the QD, followed by addition of the target
analyte that interacts with the quencher to influence the luminescence intensity. 相似文献
34.
Crespi M. S. Silva A. R. Ribeiro C. A. Oliveira S. C. Santiago-Silva M. R. 《Journal of Thermal Analysis and Calorimetry》2003,72(3):1049-1056
The thermal behavior and non-isothermal kinetics of thermal decomposition of three different kinds of composting of the USR
like: stack with drilled PVC tubes (ST), revolved stack (SR) and stack with material of structure (SM), from the usine of
composing of Araraquara city, Săo Paulo state, Brazil, within a period of 132 days of composting were studied. Results from
TG, DTG and DSC curves obtained on inert atmosphere indicated that the cellulosic fraction present, despite the slow degradation
during the composting process, is thermally less stable than other substances originated from that process. Due to that behavior,
the cellulosic fraction decomposition could be kinetically evaluated through non-isothermal methods of analysis. The values
obtained were: average activation energy, Ea=248, 257 and 259 kJ mol-1 and pre- exponential factor, logA=21.4, 22.5, 22.7 min-1, to the ST, SR and SM, respectively. From Ea and logA values and DSC curves, Málek procedure could be applied, suggesting that the SB (Šesták-Berggren) kinetic model is the appropriated
one to the first thermal decomposition step.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
35.
This paper presents a method for the energy analysis of alpha-particles emitted by transuranic elements via a novel technique
using Nuclear Tracks. The method is based on the relationship between the energy deposited in the detection material and the
diameter of the track, that is formed by chemical etching. The method involves CR-39 polycarbonate as the detector material,
one-step chemical etching after irradiation, and a digital image analysis system for automatic reading of the track diameters.
The experimental study included alpha-particles in the energy range 5.1 MeV to 5.8 MeV emitted by239Pu,241Am and244Cm. The quantitative results provide a clear signature to identify each one of the emitters based on a characteristic track
diameter. 相似文献
36.
A more consistent, straightforward, and economical protocol for generation of stannylene species and their reaction with BnBr leading to products of O-monobenzylation of diols has been set. It has shown to be specially indicated for substrates bearing vicinal trans 1,2-diol moieties on cyclohexane backbones, which are more resistant to these transformations. Such protocol has been successfully applied to myo-inositol derivatives and acyclic diols. 相似文献
37.
Summary The synthesis, characteristics and analytical applications of pyridoin phenylhydrazone are described. It reacts with copper(I) to produce an orange 11 complex (
max=450 nm,=2.1×104l· mole–1·cm–1) in aqueous ethanolic solution; it behaves as a cuproin type reagent. The orange complex can be extracted into amyl alcohol (
max=440 nm,=2.0×104l·mole–1·cm–1), and used for the spectrophotometric determination of trace amounts of copper. Interferences have been investigated.
Zusammenfassung Synthese, Eigenschaften und analytische Anwendung von Pyridoin-phenylhydrazon wurden beschrieben. Es reagiert mit Cu(I) unter Bildung eines orange gefärbten 11-Komplexes in wäßrig-alkoholischer Lösung ( max=450 nm,=2,1×104l·mol–1·cm–1); das Reagens verhält sich ähnlich wie Cuproin. Der erwähnte Komplex läßt sich mit Amylalkohol extra-hieren ( max=440 nm,=2,0×104l·mol–1·cm–1) und zur spektrophoto-metrischen Bestimmung von Kupferspuren benützen. Auftretende Störungen wurden angegeben.相似文献
38.
S.A.Vieira Filho L.P. Duarte G.D.F. Silva O.W. Howarth I.S. Lula 《Helvetica chimica acta》2003,86(10):3445-3449
3β‐(Stearyloxy)olean‐12‐ene was isolated from a hexane extract of Austroplenckia populnea Reiss (Celastraceae) leaves. The structure was solved by means of quantitative 13C‐NMR, HMBC, HMQC, COSY, NOESY, and NOE difference spectra. The mass spectrum showed an [M+1]+ ion peak at m/z 693, and the molecular formula C48H84O2 was confirmed by combustion analysis. 相似文献
39.
J. M. Hernndez Ana M. Herrera J. García‐Serrano J. F. Rivas‐Silva 《International journal of quantum chemistry》2002,88(3):342-346
Conformations of p‐methacryloylaminophenylarsonic acid (p‐MAPHA) are determined through molecular mechanics and DFT/B3LYP calculations. Solvation effects are studied within the self‐consistent isodensity continuum model (SCI‐PCM). The stationary points were found to correspond to minima as verified by the analysis of vibrational frequencies in the molecule. The molecular optical absorption was obtained by using different solvent environments. The present results are in good agreement with the available experimental data. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 相似文献
40.
Maria Fernanda Silva Estela Soledad Cerutti Luis D. Martinez 《Mikrochimica acta》2006,155(3-4):349-364
The purpose of this article is to review and evaluate cloud point extraction of metals and its coupling to different contemporary
instrumental methods of analysis. This review covers a selection of the literature published on this topic over the period
mainly between 1997 and September 2005 (consisting of 50 publications). The current state of the art for CPE concerning metals
and metal chelates is presented with special emphasis on the hyphenation of this interesting extraction/preconcentration approach
mediated by surfactants to spectrophotometry, atomic spectroscopy and separation techniques. We present contemporary CPE developments
concerning metal speciation and determination and their application to different environmental, clinical, geological and food
samples. Strategies for method development as well as future perspectives are also covered. 相似文献